1. Field
The present disclosure relates to wireless communication, and more particularly, to a method and apparatus for transmitting uplink data during a user equipment's monitoring period for receiving a particular signal in a wireless communication system.
2. Discussion of the Background
Device to device (D2D) communication is a communication scheme that has been utilized from the advent of the analog radio set. However, D2D communication in a wireless communication system is distinguished from existing D2D communication schemes.
D2D communication in a wireless communication system indicates communication in which geographically close user equipments (UEs) use the transmission/reception technologies of the wireless communication system in- or outside of the frequency band of the wireless communication system, and directly transmit and receive data between the UEs without sending data through infrastructure such as a base station (BS). This enables a UE to utilize wireless communication outside an area where wireless communication infrastructure is established, and reduces the network load of the wireless communication system.
A UE that supports D2D communication in the wireless communication system may also perform general wireless communication (that is, communication with a serving BS using a cell (carrier) provided by the serving BS). To this end, the serving BS transmits an uplink grant indicating transmission of a Physical Uplink Shared Channel (PUSCH) to a UE in the cell. The PUSCH carries an Uplink Shared Channel (UL-SCH), and uplink data (i.e., data to be transmitted to the BS) is transmitted through the UL-SCH.
However, a UE (D2D UE) that supports D2D communication needs to monitor whether a D2D signal is received from another D2D UE for D2D communication. Therefore, when the uplink grant received from the BS indicates transmission of a PUSCH during a period for monitoring a D2D signal, a UE that has a single transceiver chain (that is, a UE incapable of performing transmission and reception in parallel) may not perform either a PUSCH transmission or a D2D signal monitoring. In addition, even when a D2D UE is capable of performing transmission and reception in parallel, self-interference may occur, in which a transmission signal of the D2D UE is received by the D2D UE, when a PUSCH is transmitted during a D2D signal monitoring period.
To overcome the above described drawback, D2D communication needs a method for effectively performing a D2D signal transmission and reception by minimizing the effect on an existing LTE signal.
The D2D communication may be performed using a communication scheme that uses a non-licensed band such as Bluetooth or a wireless LAN. However, a communication scheme that uses the non-licensed band will have difficulty providing a planned and controlled service, which is a drawback. Particularly, the performance may be dramatically reduced by interference. Conversely, device-to-device direct communication may be operated or provided in a licensed band or in an environment where inter-system interference is under control, and may therefore be capable of supporting quality of service (QoS), of raising frequency utilization efficiency through frequency reuse, and of increasing communication-enabled distance.
In D2D communication in a licensed band, that is, a cellular communication-based D2D communication, a resource for D2D communication may be allocated through a BS and a cellular uplink spectrum. Alternately, uplink subframes may be used as the allocated resources.
The D2D discovery and communication may be operated independently from the cellular communication. In some instances, a Wide Area Network (WAN) signal is transmitted to a D2D UE from a BS through a DL spectrum and, at the same time, a D2D signal may be transmitted from another UE. In this instance, a UE having a single transceiver chain may be incapable of simultaneously transmitting or receiving signals through many frequency bands, which is a drawback. Therefore, the priority of signals to be processed must be determined and the handling of remaining low-priority signals must be defined.